I don’t drink much soda, I don’t buy Big Gulps, and my body mass index is right where it should be. Until the public hearing on July 24, I had largely ignored Mayor Michael R. Bloomberg’s proposed ban on large, sugary drinks because it would have no effect on my daily life. It was watching supporters of the ban struggle to articulate exactly what it would mean that motivated me to educate myself and ultimately make a movie about it. The proposal is best conveyed visually, not verbally.

To start — the proposed ban on large, sugary drinks isn’t really a ban on anything. Even if the New York City Board of Health passes the ban this coming Thursday, 7-Eleven, the ubiquitous convenience-store chain, will still be able to serve its 50-ounce Orange Explosion Slurpee, which contains 107 grams of sugar, the equivalent of nearly four full-size Snickers bars. Dunkin’ Donuts could still sell its large Vanilla Bean Coolatta (174 grams of sugar, or nearly six Snickers bars, in its 32 ounces). And if you can find a place with unlimited refills, you can still drink as much soda as you like.

The proposal would not include alcohol, fruit juices or any diet soda. Grocery stores and convenience stores would be exempt. Iced coffee and other beverages where the sugar is added by the customer would remain unaffected. Drinks are also exempt if they contain more than 50 percent milk, which would most likely allow Dunkin’ Donuts to sell Coolattas, and Starbucks Frappuccinos, as long as they can prove the milk content is there. Buying multiple 16-ounce drinks is also O.K. The ban will certainly not stop people from getting exactly what they want, as Mayor Bloomberg has made clear.

“All we’re doing here is educating,” Mayor Bloomberg said. “It forces you to see the difference.” Limiting the serving size forces people to consider how much they’re ingesting. Earlier this year the Center for Consumer Freedom ran a full-page ad in The Times saying that “New Yorkers need a Mayor, not a Nanny.” With 58 percent of adults in New York City overweight or obese and 5,800 deaths a year in the city because of obesity, it is evident that some people just aren’t responsible enough to feed themselves. This lack of nutritional responsibility affects everyone — obesity costs the city $4 billion a year in direct medical costs. A nanny is just what New York City, and the rest of America, needs.

If New Yorkers reduced portion size to 16 ounces from 20 ounces for one sugary drink every two weeks, it would collectively save approximately 2.3 million pounds over one year. This proposal could be the catalyst the city needs. Obesity is an epidemic, a crisis whose impact is widespread — over 27 percent of young adults in America are too overweight to serve in our military. Sugary drinks alone are not to blame, but they are part of the problem, and this proposal is a small step toward a solution.

Casey Neistat is a New York-based filmmaker. He has made dozens of short films released exclusively on the Internet and is the writer, director, editor and star of the series “The Neistat Brothers” on HBO. His previous Op-Docs include “Texting While Walking,” “Bike Thief” and “Taxi Lost and Found.”